I did the first time around. Sent them test shots etc., and they agreed, well, the technician did, that there was a focus problem. I've ordered the Datacolor lens calibrator to see what's what but I agree about expecting nothing short of a precision instrument for the price of the D4.
Unfortunately, I have missed my 30 day return window for the place I've ordered it from; McBain Camera out of Edmonton, Alberta. I spoke to them once about the issue and they said send it so they can play around with it before they'd contact Nikon. At the time, I was talking to Nikon about a separate issue so they said to send it in and they'd have a look at it.
I'll see what I can do but at this point, it would be nice to have it replaced.